pxr.Gf.Vec3f can be convinced to return a pointer to its float array as a (clearly bogus) string

[marktucker]

Description of Issue

Trying to cast a Gf.Vec3f to a float in python causes the Gf.Vec3f's floating point data to be interpreted as a string. I'm sure this applies to lots of other types of data casting, and lots of other pxr classes (at least within Gf). I don't really understand the mechanism here, since calling str() on a Gf.Vec3f generates a reasonable string representation of the data.

Steps to Reproduce

1. Run the following python code:
   rom pxr import Gf
   vec = Gf.Vec3f(34.56, 78.91, 23.45)
   f = float(vec)
   print f
2. This produces the following output:
   Traceback (most recent call last):
   File "converttofloat.py", line 4, in
   f = float(vec)
   ValueError: could not convert string to float: q=
   B�ѝB���A

System Information (OS, Hardware)

Tested on Linux and Windows

Package Versions

USD 20.08

[jtran56]

Filed as internal issue #USD-6284

[gitamohr]

I have mixed news on this one. I checked in a fix for how we implemented Python's buffer protocol for Python 2 for these types. It makes these examples raise TypeError, which seems good.

However, some Python 3 builtins like int() will just blindly attempt to treat bytes from objects that support the buffer protocol as string characters, ignoring what the actual data format is. I filed a Python bug for this, https://bugs.python.org/issue41707

When (if?) that Python bug gets fixed, that should resolve this for Python 3.

[monajalal]

I have an array of corner pairs (min and max from 3D BB). How can I get the minimum and maximum corners from this array? each corner is in gf vec3d format.